The present invention relates to a rotary device for a horizontal injection molding machine for turning mold portions or molded articles between the mold mounting plates about a vertical axis. The invention also relates to an injection molding machine equipped with such a rotary device.
An apparatus for holding and turning molds or mold parts in a horizontal injection molding machine is known, for example, from U.S. Pat. No. 4,330,257 and European Pat. No. EP 0 922 556 A1, with the horizontal injection molding machine having mold mounting plates between which a turret (mold center platen) is slideable in longitudinal direction of the machine and provided as mold carrier with prismatic cross section which is supported for rotation about an axis extending perpendicular to the longitudinal axis of the machine. In order to shift the turret in longitudinal axis of the machine, on the one hand, and to rotate the turret about an axis extending perpendicular to the longitudinal axis of the machine, a system is provided in which the turret is rotatably supported in carriers, with the carriers slideably guided and supported at least on both lower tie bars of the injection molding machine (U.S. Pat. No. 4,330,257) or on all four tie bars (European Pat. No. EP 0 922 556 A1). To permit a precise guidance of the carrier and of the attached turret, support and guiding elements are required which are of highly precise construction and sized in narrow tolerances and which are arranged at great distances from one another as a result of the system. Thus, this support reacts sensitively to temperature fluctuations, i.e. during cool-down period and accompanying shrinkage, the clearance in the bearings increases whereas during heating period and accompanying expansion there is a risk that the support and guiding elements get jammed on the tie bars. To prevent the latter, the tolerances in the support and guiding elements should not be too narrow, i.e. sized not too precisely. A further drawback resides in the fact that the tie bars are loaded by a significant weight (inadmissible bending) depending on the design of the turret and the carriers, and that the torques encountered during rotation of the turret must be absorbed entirely by the tie bars, resulting in particular during starting and braking of the rotational movement in significant stresses.
It would therefore be desirable and advantageous to provide an improved rotary device for horizontal injection molding machines, obviating prior art shortcomings. It would further be desirable and advantageous to provide an improved injection molding machine, equipped with a precisely supported and guided rotary device.